1. Field of the Invention
The present invention generally relates to an electronic instrument, such as a notebook type personal computer, which includes a plurality of battery packs connectable to a bus line provided in a body of the electronic instrument and which is capable of displaying a remaining battery load, and in particular, relates to a bus line address changing apparatus for changing a bus line address separately set and stored in each battery pack.
2. Discussion of the Background
An electronic instrument, such as a notebook type personal computer, utilizing a battery pack as a driving power source, is well known. Namely, such an electronic instrument includes a function of displaying a remaining load on a display section of its body by connecting a battery to a bus line provided in the body. An electronic instrument capable of utilizing a plurality of such battery packs for prolonging an operational time period and displaying a remaining load of the battery has been also known.
A background electronic instrument, such as a notebook type personal computer, as one example of a mobile information instrument, is illustrated in FIG. 4, and is provided with a body (hereinafter referred to as an instrument body) 3 having a keyboard and similar devices, and a displaying section 4 pivotally and openably supported with respect to the instrument body 3. The electronic instrument 1 sometimes includes a first battery pack 9 in a first attaching section 5, composed of a slot or similar devices, provided at a front end of the instrument body 3, and a second battery pack 11 in a second attaching section 7, e.g., a slot.
Thus, the electronic instrument 1 is driven by receiving power supplied from both of the battery packs 9 and 11. The battery packs 9 and 11 each respectively includes a pack side plus terminal 13, a pack side minus terminal 15, and a pack side communication terminal 17 for communicating with a bus line of the instrument body 3.
An indication of the power of the battery packs 9 and 11 is supplied to the instrument body 3 and a remaining power or similar information of the battery packs 9 and 11 is transmitted to the instrument body 3, when each terminal 13, 15, and 17 is connected to a later mentioned corresponding terminal provided in the instrument body 3. The instrument body 3 receives and displays the remaining load on an LCD or similar device in the display section 4. The battery packs 9 and 11 respectively each have substantially a similar constitution which allows the electronic instrument 1 to execute an ordinal operation. Thus, when both battery packs 9 and 11 are attached to the instrument body 3 and are used, an operational time period of the instrument body 3 driven by the battery packs 9 and 11 can be prolonged when compared with a case that only one battery pack is attached to the instrument body 3.
Furthermore, an electronic instrument in which only one battery pack is attached to the instrument body 3 and another is detached from its attaching section is known. In such a device, a driving device for a floppy disk or a CD-ROM is attached to the attaching section if the operational time period of the instrument body 5 is not required to be prolonged.
Further, in a background art using only one battery pack as illustrated in FIG. 5, a serial bus line 25 acting as a transmitting bus line, such as a system management bus line (hereinafter referred to as a SM bus line), for transmitting a communication signal and communication data, and a controller 27 for controlling the bus line 25, are provided in the instrument body 3. Further, a body side plus terminal 19 and a body side minus terminal 23 are provided in the first attaching section 5 of the instrument body 3 as a plus terminal and a minus terminal of the instrument body, respectively.
A body side communication terminal 21 for allowing transmission of a communication signal, communication data, and similar information with the battery pack 9 is also provided in the instrument body 3. The body side plus terminal 19 is connected to a plus side power source line 33, the body side minus terminal 23 is connected to a minus side power source line 35, and the body side communication terminal 21 is connected to the bus line 25.
In such an electronic instrument of the background art, a sequential number written in the parenthesis in FIG. 5 is utilized and represents a bus line address for an applicable device connected to the bus line 25. For instance, the bus line controller 27 (with address 0001 000) recognizes that the battery pack 9, which is one of the devices connected to the bus line 25, has an address (0001 011). A communication signal and similar information transmitted to the bus line controller 27 from the battery pack 9 may include the bus line address (0001 011). Thus, the bus line controller 27 can surely identify a communication signal transmitted from the battery pack 9 referring to the bus line address (0001 011) included in the communication signal, even if a variety of communication signals are transmitted to the bus line controller 27 from each device via the bus line 25 commonly used by the plurality of devices.
As examples of a device supplied with a power source, for instance, under control of the bus line controller 27, a cold cathode ray tube driver 29 (with address 0101 101) for illuminating a display section 4, such as a LCD, from an inside of the instrument body 3, and a card connecting terminal power source controller 31 (with address 1000 0xx), such as a PCMCIA (Personal Computer Memory Card International Association) socket, are connected to the bus line 25.
When the battery pack 9 is attached to the first attaching section 5 of the instrument body 3, each terminal 13, 15, and 17 is electrically connected to each terminal 19, 23, and 21 oppositely arranged in the instrument body 3, respectively. When the battery pack 9 and the instrument body 3 are electrically conducted in such a manner, the instrument body 3 can be supplied with electrical power from the battery pack 9 via the coupling of terminals 13 and 15, and the coupling of terminals 19 and 23. In addition, information, such as remaining load of the battery pack 9, can be transmitted to the instrument body 3 via the terminals 17 and 21.
As illustrated in FIG. 6, the battery pack 9 includes a battery 37 including a charge-impossible battery as a primary battery, such as a manganese battery or an alkaline battery, and a chargeable battery as a secondary battery, such as a nickel cadmium battery or a lithium battery, connected with each other in parallel or serially, in addition to the above-mentioned pack side plus and minus terminals 13 and 15, and the pack side communication terminal 17.
Further, a detecting section 43 for detecting a voltage or an output current or the like generated between both poles of the battery 37, an arithmetic element, such as a micro-computer, and a memorizing element, such as a memory (each not shown), are provided in the battery pack 9. The arithmetic element may calculate a remaining load of the battery 37 as a result of detection, executed by the detecting section 43, of the voltage or output current, for example, generated between the both poles of the battery 37. The arithmetic element may also control the detecting section 43 and communication of signals in a prescribed manner.
A control section 47 may have a memory for storing a bus line address (0001 011) and so on, and a bus line 45 acting as a transmission path 45 connecting the control section 47 with the detecting section and with the pack side communication terminal 17 for communicating a communication signal and similar information. The battery pack 9 may further include a plus side power source line 39 constituting a transmitting path for a power source current of the plus pole side, and a minus side power source line 41 constituting a transmitting path for a power source current of the minus pole side.
FIG. 7 illustrates an interior constitution of an instrument body 3 of the related electronic instrument to which two battery packs are attached. The first battery pack 9 is attached to the first attaching section 5 as illustrated in FIG. 5. In addition, the second battery pack 11 is attached to the second attaching section 7. Further, a selector 49, composed of a semiconductor switch or a similar device is added to a portion of the bus line 25, for selectively communicating a communication signal, such as remaining load, transmitted from the first and second battery packs 9 and 11 to the bus line controller 27.
Owing to the selector 49, either the communication signal representing the remaining load of the first battery pack 9 or that of the second battery pack 11 is transmitted to the bus line controller 27. The reason why both the communication signals representing these remaining loads can not simultaneously be transmitted and selectively transmitted to the bus line controller 27 is as follows. If these communication signals are simultaneously transmitted on a same bus line 25, a conflict of addresses occurs because both addresses for the first battery pack 9 and the second battery pack 11 are generally the same (e.g. 0001 011),. In other words, since the addresses for the battery packs 9 and 11 illustrated in FIG. 7 are the same, the bus line controller 27 cannot discriminate the above-noted communication signals, unless the selector 49 selects one of these bus line addresses and changes.
In addition, this causes a probability of an erroneous operation and an overdriving of the bus line controller 27. Then, the selector 49 may select a communication signal, and transmit the selected communication signal to the bus line controller 27 so that the bus line controller 27 does not erroneously operate and overdrive.
Further, an additional problem occurs such that a hardware construction of the instrument body 3 and a control use software for the bus line controller 27 and similar devices become complex due to having to provide the selector 49 in the instrument body 3. To resolve such problems, it is possible to simply differentiate addresses for the battery packs 9 and 11, respectively.
However, the bus line controller 27 cannot recognize a battery pack attached to each attaching section if a bus line address as an ID for discrimination of each battery pack is optionally changed at the battery pack side because the bus line controller 27 generally recognizes that a bus line address of a device, i.e., a battery pack 9, attached to the first attaching section 5 is (xxxx xxx), and that of the battery pack 11 attached to the second attaching section 7 is (yyyy yyy). Accordingly, when an address for each battery pack is differentiated at the battery pack side, an address for a battery pack attached to the first attaching section 5 should be limited to (xxxx xxx), and that for a battery pack attached to the second attaching section 7 should be limited to (yyyyy yyy).
However, when a bus line address for each battery pack 9 and 11 is differentiated (at the battery pack side), a single battery cannot be used for both the battery packs, i.e. both of the battery packs respectively cannot be equally constituted and common. This may result in requiring two kinds of battery packs when designing, producing, distributing, and stocking, and may be a cause of increasing cost of the electronic instrument.